Hydroxy lactones with the gem-dimethylcyclohexane system – Synthesis and antimicrobial activity

Two new lactones comprising the gem-dimethylcyclohexane ring: 2-chloro-5,5-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one and 2-bromo-5,5-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one as well as the already known 2-iodo-5,5-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one, were obtained from (6,6-dimethylcyclohex-2-en-1-yl)acetic acid. These lactones were used as substrates for the screening of biotransformation by whole cells of nine fungal strains (Fusarium species, Syncephalastrum racemosum and Cunninghamella japonica). Some of these microorganisms (mainly Fusarium species) transformed all three lactones during the hydrolytic dehalogenation into 2-hydroxy-5,5-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one. It is worth noting that two microorganisms (Fusarium culmorum and Fusarium scirpi) converted iodolactone with very high enantioselectivity (75.1% and 91.6%, respectively). The (+) isomer of hydroxy lactone was preferred. At the last step the hydroxy lactone obtained during biotransformation was examined for its biological activity against bacteria, yeasts and fungi. It was found that this compound inhibits growth of some tested microorganisms.     

Heat kernels on metric spaces and a characterisation of constant functions

Using the Dirichlet forms theory, we prove that when the locally compact measure metric space (X,,m) is the state space of a Markov process with transition density p(t,x,y) bounded from the above by where is a function satisfying certain integrability condition, then the following statement holds: when u L²(X) and then u is a constant function.This work is partially supported by a KBN grant no. 2-PO3A-028-22.Mathematics Subject Classification (2000): primary 60J35, secondary 46E35     

The surface tension and density of the Cu-Ag-In alloys

The surface tension and the densities of the Cu-Ag-In alloys have been measured by means of the sessile drop method. The density of these alloys depends linearly on temperature in the case of all the investigated compositions. The surface tension shows a linear dependence on temperature except for the lowest temperatures. For most of the alloys, the surface tension at the lowest temperature is lower than that predicted by the straight line. The experimental values of the surface tension of the Cu-Ag-In alloys are compared with those computed from the model, and quite good agreement is observed.     

13C CP MAS NMR and GIAO-CHF calculations of coumarins

13C cross-polarization magic-angle spinning NMR spectra were recorded for a series of solid coumarins. Ab initio calculations of shielding constants were performed with the use of GIAO-CHF method. The combined CPMAS NMR and theoretical approach was successful in characterizing solid-state conformations of coumarins; a relationship sigma (ppm) = -1.032 xdelta + 205.28 (R(2) = 0.9845) can be used to obtain structural information for coumarins, for which solid-state NMR or crystal structure data are not available.     

Computer simulation and optimization of preparative thin-layer chromatography under conditions of isocratic and stepwise gradient elution

Summary An equilibrium sandwich chamber for continuous thin-layer chromatography was used to study overloaded systems. Mixtures of two or three dyes were used as the model samples, and wide starting zones were formed (volume-overloaded systems). The movement of the zones was recorded during continuous elution. The effect of sample volume and the mode of development (isocratic or gradient) on the maximum separation yield was investigated. A computer program was developed for the calculation of the final R_F values for the front and rear edges of the bands.Satisfactory agreement was found between the experimental R_F values of zone boundaries and the values predicted by computer simulation.Presented at the 2nd International Symposium on Preparative and Up-Scale Liquid Chromatography, February 1–3, 1988, Baden-Baden (FRG).     

Functional derivative δE/δρ in calculation of chemical potential for the Kohn–Sham electronic system

A method for finding the chemical potential for an electronic system with density ρ = Σ_ρi represented within the Kohn–Sham approximation is proposed. To find the chemical potential of the system under consideration, we propose to refer to the definition μ = δE/δ_ρ and to apply the mathematical properties of functional derivatives. Particularly, in the case examined, the result μ = μ( r ) ≠ const has been obtained, which may be explained in the framework of the calculus of variation. Taking the limit lim_r→∞ μ( r ) as the best approximation to the proper equilibrium chemical potential of a free atom, one obtains μ = ?I, where I denotes first ionization energy. A possibility of further applications of the proposed method in relation to crystalline systems is also discussed. © 1994 John Wiley & Sons, Inc.     

The Synthetic Utility of Amide and Amidine Derivatives Containing Polycarbonyl Moieties in the Synthesis of β-Aminoenones

Summary.  The application of derivatives of the easily decomposing weak bases formamide, semicarbazide, urea, or formamidine in the synthesis of β-aminoenones is described. These compounds readily undergo transamination with strong bases, thus opening the way to various heterocyclic compounds. Received July 16, 2001. Accepted (revised) September 17, 2001     

Charge-assisted N(+)–H···(−)S hydrogen bonds in the crystal structure of selected diammonium thiophenolates

New salts of thiophenol with three flexible aliphatic diamines H₂N(CH₂)_nNH₂ (n = 2, 4 and 6) have been synthesized and characterized by elemental analyses, IR spectroscopy and X-ray crystallography in order to analyze their supramolecular architecture. Structural analyses indicate that in the crystals, proton transfer has occurred, with the –SH group giving ⁽⁺⁾N–H···S^(?) hydrogen bonding interaction. The structure of compound 1 exhibits a two-dimensional network and compounds 2–3 a three-dimensional supramolecular networks, and each of them is based on hydrogen bonds and CH···π interactions. The transfer of proton from the thiol to the diamines was confirmed by the solid-state FTIR spectra of 1–3.

     

Chemical composition and antioxidant,antibacterial activity of Cirsium rivulare (Jacq) All. roots

The mixture of three phytosterols (campesterol, stigmasterol and β-sitosterol), β-sitosterol 3-O-glucoside and syringin were isolated from hexane and methanol extract of Cirsium rivulare roots after chromatographic separation. The main component of the source was syringin which was obtained with the yield 0.08% of the dry source. In hexane extract, the qualitative and quantitative composition of fatty acids was determined. The predominant component was linoleic acid (23.31 mg/g of extract). The extracts showed antioxidant activity. The ability to scavenge DPPH? free radical was in correlation with appointed total phenol content. The not-defatted methanolic extract was the most active. Hexane and defatted methanol extracts showed moderate antibacterial activity against G(+) and G(?) strains with MIC and MBC ranged from 25 to 200 μg/mL.     

The influence of immersion and contact ultrasound treatment on selected properties of the apple tissue

Ultrasound (US) treatment is considered to be one of the most promising non-thermal technology used in the food processing. The food-related applications of this technique are linked to the analytical and technological purposes. The ultrasound waves in the food can cause the formation of micro-channels due to the systematic and alternating compression and decompression of the material (so called “sponge effect”). Additionally, in liquids the ultrasound application can cause the cavitation which can modify the food properties as well. Hence, due to its mechanism, the ultrasound treatment can also improve the extraction of pigments, aromas or antioxidants from the food matrices.